This invention relates to the field of pavement reinforcement. More particularly, the invention relates to means and methods for cutting aligned sets of slots in pavement to accommodate the insertion of steel dowel bars for reinforcing faulted areas adjacent joints in the paving.
Pavement on streets, highways, air strips and the like is subject to wear and deterioration from, among other forces, the repeated travel of vehicles thereon. In the case of highways, the majority of the wear is known to follow a particular pattern. After the passage of a multitude of vehicles along a highway, a wear pattern develops and is evidenced by a pair of indentations or wheel paths in each lane of the pavement.
Another kind of deterioration which is prevalent on well-traveled strips of pavement is faulting at the expansion joints. Where the wheel paths intersect the transverse joints, the pavement is known to suffer repeated heavy loading due to the passage of traffic thereover. As a result, the pavement around the transverse joint is subject to a type of premature fatigue failure known as faulting. Load transfer restoration (LTR) is known to improve the load transfer across a joint and reduce the rate of future fault development. Load transfer describes the distribution of load across a transverse joint of pavement under vehicular traffic. Aggregate interlock, dowel bars and subbase support influence the degree of load transfer. The ability of a joint to distribute load is fundamental to its performance and is characterized by joint effectiveness measurements. Poor load transfer is typically evidenced by a loss of structural integrity such as faulting and, if not corrected, cracking and crumbling of the pavement near the joint.
Restoring load transfer at joints is necessary to stop pavement deterioration. It may be necessary because a designer omitted dowels in an existing pavement and subsequent joint faulting has become a problem or deicing chemicals have corroded unprotected dowels. In either case, load transfer restoration (LTR) places good mechanical load transfer in the joint. Undoweled joints lose load transfer faster than those with dowels under similar traffic. A joint effectiveness of 50 percent or more is considered adequate for typical heavy truck loadings. LTR improves load transfer and reduces the rate of future fault development across joints or transverse cracks on concrete pavements.
Backfill refers to the material used to fill in the slot after the dowel has been installed. A good bond between the backfill and slot/core walls is essential for LTR performance. The bond helps carry the load in shear across the joint. Therefore, careful preparation of the slot is essential.
The slots for dowels are cut in the wheel paths, parallel to the pavement centerline and with each other. Careful alignment is essential for optimum performance. Conventionally, the pavement surface is ground after the cutting, chipping, and cleanout and backfilling processes.
A common load transfer assembly includes a horizontally disposed oiled steel dowel bar. The typical heaving truck loading often necessitates the use of a plurality of dowel bars to appropriately transfer the load across the wheel path. At least three dowels in each wheel path are known in the art to be recommended on roadways subject to heavy truck traffic. Because existing highways can be easily retrofitted with steel dowel bars at the transverse joints, dowel bar retrofitting provides a quick and inexpensive alternative to completely removing the road surface and repaving it with load transfer assemblies embedded therein.
Conventionally, contractors have employed saws equipped with gang-mounted diamond-impregnated blades to cut a single slot of the desired width and location at one time. These saws are typically rotatably mounted to a frame. The whole machine, saw and frame included, must be moved to affect the desired cut. Such saws have typically been limited to cutting only one side wall of the slot at a time or cutting both side walls of a single slot at one time. Such an arrangement may provide the necessary alignment between the side walls of a single slot, but does not provide the necessary alignment between a set or group of slots.
In conventional saws having one to four blades, cooling and safe operation are problems. Some saws spray liquid on the blade for cooling it, resulting in slurry material which presents unsafe conditions for the operator and passersby, including vehicular traffic.
Therefore, it is the objective of this invention to provide means and methods for simultaneously cutting a plurality of slots at joints in pavement to form an aligned group of slots suitable for the retrofit installation of dowel bars for load transfer restoration.
It is a further objective of this invention to provide a quick and efficient means and method for load transfer restoration of pavement.
It is a further objective of this invention to provide a means for cutting slots in pavement wherein the cutting blade is movable vertically and horizontally during the cutting process without moving the vehicle to which the cutting blade is mounted.
It is a further objective of this invention to provide a means for setting the width between the right and left set of slots in a group of aligned slots.
It is a further objective of this invention to provide means for canting the cutting blades to ensure square entry of the blades into the pavement, even when the pavement surface is not flat and level.
It is a further objective of this invention to provide an aligned group of slots, each slot side walls and a bottom which are well adapted to have a plurality of chairs snugly fit between the side walls of each slot for accurately positioning and supporting a dowel bar which is snapped in the chairs.
It is a further objective of this invention to provide a means for cutting slots in pavement wherein the blade assembly is movable horizontally, vertically, and laterally relative to the vehicle frame to which the blade assembly is mounted.
It is a further objective of this invention to provide a means of adjusting the vertical height of the blade and setting its depth of cut.
It is a further objective of this invention to provide means and methods for joint load transfer restoration of pavement which can be accomplished with a minimum of labor.
It is a further objective of this invention to provide a safe and efficient means and methods for cutting slots in a pavement surface.